1. Field of the Invention
This invention generally relates to the field of electronic input devices, and more particularly relates to touchpad input devices.
2. Description of Related Art
Space on electronic devices, particularly on small, portable electronic devices, is scarce and valuable. Furthermore, electronic devices, especially portable devices, are continually decreasing in size and weight. At the same time, they are increasing in complexity and functionality. Electronic devices include, for example, laptop computers (also referred to as notebook computers), desktop computers, keyboards, monitors, personal digital assistants/electronic organizers, communication devices such as cellular phones and pagers, navigation devices such as global positioning systems (GPS's), medical devices, data collection devices such as bar code scanners, and video game devices. Most electronic devices feature a display that presents the user with a graphical user interface, which requires various input tasks such as cursor movement, scrolling, and zooming in order to navigate within the display. Well-designed input devices are critical for effectively controlling the numerous functions of electronic devices and navigating increasingly complex graphical displays. However, a major challenge is confronted in designing input devices that are easy to use, comfortable for the user, and accurate while at the same time do not require any additional dedicated housing space. Such input devices that do not require additional dedicated housing space allow the overall size and weight of an electronic device to be minimized, which is highly desirable for consumers, particularly in the case of portable devices. Even in non-portable devices, such as desktop computers, it is highly desirable to minimize the overall size of the device so that it occupies a minimum of desktop space, for example.
Current examples of input devices include the mouse, touchpads, trackballs, directional keys, selector buttons, toggle switches, joysticks, rotating dials, and the small, fingertip-actuated, isometric joystick stubs frequently located between the keyboard keys of laptop computers. The mouse, commonly used with desktop computers, is typically unfeasible for use with portable devices, which require an integrated input device. Integrating these various input devices into electronic systems, particularly portable electronic devices, typically requires additional housing space to be dedicated to the input device, necessitating an increase in the overall size and weight of the electronic device.
Touchpad input devices, also referred to as touch sensor input devices, are used in such devices as the GLIDEPOINT input pad, the PALM PILOT, and various laptop computers, in which the touchpad is typically located on the face of the device, such as below the keyboard in laptop computers or below the display in personal digital assistants such as the PALM PILOT. Touchpad input devices typically use technology such as capacitive sensing technology to provide a touch-sensitive surface. The user merely touches the touchpad, typically with a finger, and the contact from touching is detected and translated into electrical input signals. The outer edges of some touchpads are programmed for up-down and left-right scrolling functions, while the center of the touchpad may be used for controlling a cursor's position or for entering letters, numbers, or other symbols. However, the distinction between the different functional areas of such touchpads is not clear. Furthermore, the size of the different functional areas of the touchpad is limited by the size of the touchpad itself and, generally, touchpads must be small compared to the overall size of the electronic device due to inefficient use of housing space by the input device, and the need to minimize the overall size of the electronic device. Smaller functional areas of the touchpad result in limited functionality of the touchpad, reduced input resolution, and less precise control, such as when controlling cursor movements in a graphical display. Furthermore, such small touchpads are typically awkward and inefficient to use.
Touchpad input devices generally use either capacitive (i.e., charge storing), resistive, or semiconductive sensing technology to detect user input, i.e., touch. Capacitive sensing technology is the most common. Generally, in capacitive sensing technology, oscillatory circuits at each corner of the touchpad are connected to electrodes to provide a constant voltage across the touchpad. The touchpad has a capacitive layer that may be composed of, for example, indium tin oxide. Contact with the touchpad, such as by touching with a finger or other conductive object, draws current to the point of contact. The amount of current drawn is proportional to the distance of the contact from the sides of the touchpad. The variation in current flow results in a corresponding change in the electrical frequencies of the oscillatory circuits; this change in frequency can be translated into x and y coordinates, thereby precisely establishing the position of the contact. This information can then be relayed through a control circuit to generate corresponding output, such as cursor movement or scrolling within a display. In addition to touchpads, capacitive sensing technology is also commonly used in touchscreens, such as in kiosks, where it provides an effective and easy to use means for selecting desired functions depicted within a display, such as to obtain information.
Resistive touchpads work in much the same manner as capacitive touchpads, except that changes in resistance, rather than capacitance, are detected. Semiconductive touchpads generally feature semiconductive layers below the surface of the touchpad that can sense pressure applied toward the touchpad by sensing increased contact between the semiconductive layers. Another type of touchpad is the proximity sensitive, or charge transfer, pad that does not require actual physical contact for input. Rather, proximity sensitive pads can sense the electric charge of a finger or other conductive object that is in close proximity, but not necessarily in contact with, the pad.
Non-contact electric-field-based position sensors allow the position of a hand or piece of conductive material to be determined at some distance from the transducers. Similarly, optical sensors can determine the position of visible objects at a distance. Any of these sensing means may be used as input to a device by which the user can manipulate the actions of the device by position or movement of a hand or other object. Thus the touchpad as described herein consists of the area or region in space over which position and motion can be sensed, and is not limited to the sensing apparatus itself or its immediate proximity.
Generally, proximity sensors are well known. For example, teachings of electric field detection of a user's finger, hand, etc, may be found in the following U.S. patents: U.S. Pat. No. 5,914,701, entitled “Non-Contact System For Sensing And Signalling By Externally Induced Intra-Body Currents”, and U.S. Pat. No. 5,844,415, entitled “Method For Three-Dimensional Positions, Orientation And Mass Distribution”, and U.S. Pat. No. 6,066,954, entitled “Apparatus For Resolving Presence And Orientation Within A Defined Space”, and U.S. Pat. No. 5,914,610 entitled “Apparatus And Method For Characterizing Movement Of A Mass Within A Defined Space”. The teachings of the above referenced U.S. patents is hereby incorporated by reference. The above referenced U.S. patents illustrate how the position and motion of a user's hand or finger can be detected without contact.
Conventionally, input devices, particularly touchpads, are located on the face of a device housing, typically below the keyboard or graphical display. However, positioning an input device at such a location requires additional housing space to be dedicated to the input device, necessitating an overall increase in size and weight of the electronic device. Furthermore, such an arrangement may be unnatural and uncomfortable for the user. Thus, conventional input devices do not effectively fulfill the two design objectives of providing for efficient input and minimizing the overall size and weight of the devices.
Therefore a need exists to overcome the problems with the prior art as discussed above, and particularly for an input device that is accurate and easy to use, that exploits natural hand positioning and hand movements for input, and that makes use of previously unused space on a device housing, rather than requiring additional housing space dedicated to the input device, in order to minimize the overall size and weight of an electronic device.